The invention relates to a method for performing frequency selective control channel scheduling in networks using an OFDM spectrum according to the preamble of claim 1, a mobile terminal according to the preamble of claim 9, a base station according to the preamble of claim 10, and a network according to the preamble of claim 11.
Orthogonal Frequency Division Multiplexing (OFDM) radio systems are currently under discussion in many places as e.g. in 3GPP Technical Specification Group (TSG) Radio Access Network (RAN1).
OFDM is a multi-carrier modulation technique. The data is divided among a large number of closely spaced subcarriers. Several bits of a bit stream are mapped on one subcarrier by modulating the complex amplitude by e.g. QPSK (QPSK=Quadrature Phase Shift Keying), 16-QAM or 64-QAM (QAM=Quadrature Amplitude Modulation).
Frequency-selective resource allocation algorithms such as adaptive modulation, subcarrier allocation and power control can enhance the performance of OFDM downlink systems. According to channel conditions which are reported from a mobile terminal as e.g. a UE (User Equipment) to a base station as e.g. a Node B the resources can be optimally distributed to achieve maximal throughput.
In the legacy OFDM systems such as WLAN (WLAN=Wireless Local Area Network) the resource scheduling is performed on a frequency non-selective basis. Therefore, there is no need to measure the channel conditions frequency selective in WLAN systems. The Signal-to-Interference Ratio measurement as the basis for channel quality estimation in High Speed Downlink Packet Access (HSDPA) using Code Division Multiple Access (CDMA) is frequency independent, too.
A radio access network in which a frequency selective resource scheduling will be implemented is described in the technical report 3GPP TR 25.813 V0.1.0 (2005-11).
The object of the invention is thus to estimate the channel conditions dependent on the frequency to allow for frequency-selective resource allocation in networks using an OFDM spectrum.
This object is achieved by a method according to the teaching of claim 1, a mobile terminal according to the teaching of claim 9, a base station according to the teaching of claim 10, and a network according to the teaching of claim 11.
The main idea of the invention is to provide a mobile terminal with coded signals on several subcarriers to perform a measurement of the channel conditions without blocking extra resources for data transmission. More precisely, the mobile terminal has to measure the channel conditions, e.g. in the form of a Signal-to-Interference Ratio (SIR) or based on path loss measurements, on several predefined subcarriers, and in order not to spend extra frequency resources for the measurement of channel conditions, it is proposed to use for this purpose a frequency selective shared control channel with a special signaling structure. Such a frequency selective shared control channel only uses dedicated OFDM symbols or subcarriers that are chosen based on the channel quality. Preferably, this special structure guarantees a multiple use of the frequency selective shared control channel for signaling and for data transmission.
Further developments of the invention can be gathered from the dependent claims and the following description.